Inserted blade hob



NOV. 2, 1954 PE 2,693,020

INSERTED BLADE HOB Filed Aug. 30, 1951 v IN VEN TOR. fld 7'2] Z/7% ray United States Patent Ofilice 2,693,020 Patented Nov. 2, 1954 INSERTED BLADE HOB Harry Pelphrey, Detroit, Mich assignor to Michigan Tool Company, Detroit, Mich., a corporation of Delaware Application August .30, 1951, .Serial No. 244,379

4 Claims. (Cl. 29-105) This invention relates to an improved hob assembly and particularly relates .to inserted blade hobs and to the method of manufacturing the same.

Heretofore hobs have been fabricated from a single blank of material and it is commonly recognized that one disadvantage of such hobs is that the entire hob must be discarded when only one of the teeth becomes damaged. This disadvantage is particularly pronounced and expensive in the case of large diameter hobs. Additionally, it is recognized that the teeth of large diameter hobs possess less desirable strength characteristics than the teeth of smaller hobs because the teeth are subjected to less cold working during manufacture. Furthermore manufacturing difiiculties and expenses are disproportionately increased as the size of the hob increases.

It is, therefore, one of the objects of this invention to provide a hob assembly of the inserted blade type which may be readily manufactured in large sizes.

A further object of this invention is to provide an improved inserted blade hob wherein the blade is rigidly secured to the hob body .and yet may be removed and replaced when desired.

Another object of this invention is to provide a novel attachment means for detachably securing hob blades positively and rigidly to hob bodies.

A still further object is to provide an improved method for manufacturing the improved hob assemblies of this invention.

Still another object is to provide a novel attachment means for detachable hob blades which does not require the maintenance of close tolerances or the production of exacting parts.

Other objects and advantageous features of the invention will be specifically pointed out or will become apparent as the full description of the invention is developed when taken in conjunction with the accompanying drawing wherein:

Figure 1 is an elevation view of an inserted blade hob embodying the features of this invention.

Figure 2 is a sectional view of the structure illustrated in Figure 1 taken along the line 22 thereof.

Figure 3 is a view partly in elevation and partly in section similar to the structure illustrated in Figure l and showing a modification thereof.

Figure 4 is a sectional view of the structure illustrated in Figure 3 taken along the line 4-4 thereof.

Referring more particularly to the drawing, there is illustrated a hob, generally designated 10, having a body portion 11 of generally disc shape and having a centrally located aperture 12 therein adapted to permit the mounting of the hob on a rotatable shaft. Means for securing hob 10 to the rotatable shaft is provided in the form of key-way 13. On the periphery of body portion 11 there is provided a plurality of longitudinally extending recesses 14 which are adapted to receive individual hob blades. Positioned within peripheral recesses 14 are unitary hob blades 17. The blades 17 are elongated rectangular-shaped members having a body portion 19 adapted for engagement with the wall portions and 15 of recess 14 and a plurality of teeth 18 on the periphery thereof.

It will be appreciated that in order for hob blades 17 to function in a manner comparable to a single piece hob, it is vital to provide a positive seating for the blades and means for maintaining that seating rigidly during use. It is furthermore desirable that the seating means be of a character that is not dependent upon the mating of precision-mac'hined surfaces and the like, but rather will permit broad tolerances and ease of manufacture. To this end there is provided, in accordance with this invention, securing means for blades '17 which uniquely exhibits these desirable features as Well as others. As .is illustrated in Figures 1 and 2 the sealing means may comprise a longitudinally extending groove 16 positioned in wall 15 of recess 14, a correspondinggroove 20 positioned in 'body portion 19 of blade 17 adapted to register with the groove in wall 15 and a holding or securing means 21 mounted in the bore defined by the cooperating groove surfaces 16 and 20. As illustrated grooves 16 and 20 are semicylindrical in shape, but it will be appreciated that the shape of the grooves is .not critical and that square grooves, 'V-shaped grooves, etc. are equally operative.

In the assembly of the parts comprising the securing means, it is to be noted that grooves 16 and 20 may be manufactured to loose tolerances inasmuch as all that is necessary is that they register within about to The holding means 21 is, before assembly, a stud having a diameter somewhat smaller than the bore defined by cooperating grooves 16 and 20, for example, about l/ to smaller. Blade 17 is positioned in recess 14 and stud 21 is inserted in the bore. The end extremities of stud 21 are contacted with a pressure applying means and stud 21 is cold upset within the bore while blade 17 is rigidly held in proper position. Pressure is slowly applied to stud 21 until the bore is intimately filled positively locking blade 17 and body 11 into unitary relationship. Pressure on the ends of stud 21 is then increased and applied intermittently, if desired, until head port-ions 22 and 23 are formed on either side of body 11. Head portions 2.2 and 23 are in pressed contact with body 11 and overlap the axial end portions of blades 17.

The slow application of force axially of the stud 21 is essential for the successful accomplishment of the pur poses of this invention. The use of intermittent blows such as are commonly employed in riveting is not recommended since the head portions are thereby formed.

before the shank portion of stud 21 is cold upset and the bore remains incompletely filled. A wide variety of materials are suitable for use as the holding means and, in general, any common metallic material having a Rockwell C hardness lower than about 25 may be employed. Materials illustrating this class of metallic materials which are successful for this purpose include brass, bronze, and other copper-base alloys, annealed low carbon steel such as SAE number 1110, etc.

It will be appreciated that this procedure allows the formation of larger hobs than have been previously considered economically feasible and when using blades of high speed steel provides blade portions which are inherently superior to previous hobs due to the greater amount of mechanical working to which the teeth of the blades are subjected. It is thought that the increased amount of cold working enhances the even distribution of carbides throughout the matrix thereby increasing the strength and fatigue characteristics of the metal in the tooth portions of the blades.

Body member 11 may be suitably fabricated from any of the wide variety of hardening tool steels which are preferably heat treated to a Rockwell C hardness of 5358 while the blade portion 17 may be made from high speed steel, standard cutting tool cast alloys or cemented carbides. The structure illustrated in Figures 1 and 2 has been found to be particularly advantageous for blades of the high speed steel type. For blades fabricated from the cast alloys or cemented carbides, having extremely high hardnesses, the structure illustrated in Figures 3 and 4 is preferred.

In Figure 3, there is provided a hob body 26 which is similar to that illustrated in Figure 1 but differing therefrom .in that the peripheral recesses 27 are somewhat wider' and adapted to accommodate hob blades 28 as well as wedge members 29. Recess 27 has one wall thereof provided with a longitudinally extending groove 30, and wedge member 29 is similarly grooved along its length to register with groove 30. Blade 28 has its forward or cutting side 32 tapered so that the outer portion adjacent the cutting surface is slightly thinner than the portion positioned in the recess 27. Wedge 29 has its ungrooved face tapered to conform to the taper which is provided on the surface 33 of blade 28. The degree of angularity is not critical and may satisfactorily vary, for example, between about 3 and degrees.

As may best be seen in Figure 4, the hob of this modification may be assembled by providing end plates 34 which are adapted to abut the axial ends of blade 28 and wedges 29 thereby providing support and insuring rigid positioning of wedges 29. End plates 34 are provided with apertures 35 aligned with the bore formed by cooperating grooved surfaces 30 and 31 and blades 28 are secured rigidly in place by inserting into the said bore a rivet member 36 and upsetting the same in situ in a manner comparable to that described hereinabove. It will be readily apparent that this modification is particularly advantageous when employing cast alloy or cemented carbide blades which are extremely difiicult to satisfactorily groove, and furthermore that it enables the use of thinner and less expensive blades. It is, of course, to be realized that blades of cast alloys and cemented carbides may be fabricated with sutficient thickness such that the structure of Figures 1 and 2 may be employed.

While only two embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that various changes, additions, omissions and substitutions may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a hob assembly, the combination of a hob body having a plurality of peripheral longitudinally-extending blade recesses therein, hob blades in said recesses, means fastening each said blade individually in its recess including a longitudinally extending groove in the Wall of said recess and a longitudinally extending registering groove associated with said blade, said registering grooves defining a bore, and means positioned in the bore defined by said registering grooves to secure said blade in said recess, said means consisting of a member having an expanded shank portion in said bore intimately filling the same and having enlarged head portions in pressed engagement with the opposite sides of said body holding said blades solidly in said body.

2. A hob assembly comprising a centrally apertured cylindrical body portion having a plurality of longitudinally-extending blade receiving recesses in the periphery thereof, each said recess carrying a longitudinal groove in one wall thereof, hobbing blades positioned in said recesses, said blades being secured in said recesses by wedge members having a longitudinal groove in one side thereof adapted to register with the groove in said wall, the other side of said wedges being tapered conjugate to the taper on one surface of said hobbing blades, and a stud member in the bore defined by the said registering groove surfaces, said stud having an expanded shank portion conforming to the bore defined by said registering groove surfaces and said stud having enlarged head portions in pressed engagement with the opposite sides 8f ({he said hob body holding said blades solidly in said 3. A hob having a generally disc-shaped body having a plurality of peripheral blade receiving recesses therein, hob blades in said recesses, means fastening each blade individually in its recess including registering grooves, one in the side of the blade and one in the side of the recess and a rivet in, and extending through, each pair of cooperating grooves, said rivets having an expanded shank portion intimately filling said grooves and head portions on opposite sides of the hob body, said shank portion conforming exactly to the bore form defined by the said cooperating groove surfaces and said head portions being in pressed engagement with the axial end portions of said blades and the sides of the said hob body to hold the said blades solidly in the said body.

4. A method for forming an inserted blade hob which comprises the steps of (1) providing a generally discshaped body having a plurality of blade receiving recesses on the periphery thereof, one wall of said recesses having an axially extending groove therein, (2) providing blades adapted to be positioned in said recesses, each said blade having a longitudinal groove registering with the groove in each said recess, the cooperating groove surfaces defining a bore, (3) positioning the said blades in the said recesses, (4) inserting a member into the said bore capable of being cold upset and having a diameter slightly less than the diameter of the said bore and (5) cold upsetting the said member in the said bore to intimately fill the same and continuing the cold upsetting to form head portions on the said member.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,278,629 Francis Sept. 10, 1918 1,874,536 Irwin Aug. 30, 1932 2,113,598 Mueller Apr. 12, 1938 2,499,994 Hart Mar. 7, 1950 2,567,167 Drader Sept. 11, 1951 

